The present technology relates to an inner-wall measuring instrument capable of, for example, measuring an inner wall of an engine cylinder or the like and to an offset-amount calculation method applicable thereto.
From the past, measuring instruments including a plurality of types of probes have been used. For example, Japanese Patent Application Laid-open No. 2009-216548 (hereinafter, referred to as Patent Document 1) has described a surface profile measuring instrument including a probe holder to which a laser displacement probe, a touch probe, and an image probe are attached. In this surface profile measuring instrument, the probe holder is provided with a probe selection mechanism. The probe selection mechanism is capable of selectively moving a probe to be used for measurement to a predetermined probe selection position and retracting the other probes from the probe selection position. With this, it becomes possible to maintain measurable ranges in common with the probes without increasing the size of the instrument (paragraphs [0015], [0016], and [0021] in specification, and FIGS. 3 and 4, etc. of Patent Document 1).
Moreover, Japanese Patent No. 5350169 (hereinafter, referred to as Patent Document 2) has described an offset-amount calculation method, in which, regarding a surface profile measuring instrument including a contact-type detector including a stylus and an image probe, an offset amount between the contact-type detector and the image probe can be correctly determined (paragraphs [0028] to [0032] and [0021] in specification, FIGS. 8 to 10, etc. of Patent Document 2).